The present invention relates generally to an apparatus for suppressing noise which radiates from the ignition system of an internal combustion engine, and more particularly relates to an apparatus for suppressing noise which generates from the electrodes of the distributor rotor and the stationary terminals, which are located in the distributor.
The igniter in which an electric current has to be intermitted quickly in order to generate a spark discharge, radiates the noise which accompanies the occurrence of the spark discharge. It is well-known that such noise disturbs radio broadcasting service, television broadcasting service and other kinds of radio communication systems and, as a result the noise deteriorates the signal-to-noise ratio of each of the above-mentioned services and systems. Further, it should be recognized that the noise also causes operational errors in electronic control circuits which will undoubtedly be more widely and commonly utilized in the near future as vehicle control systems, for example E.F.I. (electronic-controlled fuel injection system), E.S.C. (electronic-controlled skid control system) or E.A.T. (electronic-controlled automatic transmission system).
As a result of such errors traffic safety will be threatened. In addition, the tendency for an electric current flowing in the igniter to become very strong and to be intermitted very quickly to generate a strong spark discharge, will become a common occurrence because of the increasing emphasis on clean exhaust gas. However, a strong spark discharge is accompanied by an extremely strong noise which increases the previously-mentioned disturbance and operational errors.
For the purpose of suppressing the noise various kinds of apparatus or devices have been proposed. However, most of the proposed apparatus or devices are too expensive for practical use in mass-produced vehicles. Further, these apparatus or devices are not, in practice, reliable. One prior art example which is considered to have practical value, is provided by the Japanese Patent Publication No. 48-12012. In this Japanese Patent, the spark gap between the electrodes of the distributor rotor and the stationary terminal in the distributor is selected to be between 1.524 (mm) and 6.35 (mm), which is wider than the spark gap used in the typical distributor.
In the prior art, there are three kinds of typical apparatus for suppressing noise. A first typical one is the resistor which is S, L, or K-shaped and is attached to the external terminal of the spark plug, wherein, in some cases, the resistor is contained in the spark plug and hence, is called a resistive spark plug. A second typical one is also a resistor which is inserted in one portion of the high tension cable and hence, is called a resistive high tension cable. A third typical one is the noise suppressing capacitor. However, the prior art apparatus for suppressing noise, mentioned above, are defective in that although they can suppress noise to a certain intensity level, that level is not less than the noise level which must be suppressed in the fields of the above-mentioned broadcasting services, radio communication systems and electronic-controlled vehicle control systems. Moreover, the noise suppressing capacitor has no effect on high-frequency noises.
Therefore, it is the principal object of the present invention to provide an apparatus for suppressing noise and to do so more effectively than that of the prior art.
Another object of the present invention is to provide a highly reliable apparatus for suppressing noise at a moderate price for use in vehicles which are mass-produced.